Automated longitudinal position translator for ultrasonic imaging probes, and methods of using same

ABSTRACT

A longitudinal position translator includes a probe drive module and a linear translation module. The probe drive module is coupled operatively to an ultrasonic imaging probe assembly having a distally located ultrasound transducer subassembly in such a manner that longitudinal shifting of the transducer subassembly may be effected. The probe drive module is preferably mounted to the linear translation unit so as to be moveable between a condition whereby longitudinal shifting of the transducer subassembly can be conducted either manually or automatically. When in the automatically-operable condition, the probe drive module will be engaged with a motor-driven screw associated with the linear translation module so as to cause the probe drive module to be longitudinally displaced at a constant motor-driven rate. In this manner, the distally located ultrasound transducer is longitudinally shifted during an ultrasound scan of surrounding intravascular (or other) tissue to thereby allow axially-spaced 360 data sample “slices” of the surrounding tissue to be obtained. The data samples may then be reconstructed into a three-dimensional or other two-dimensional representations of the scanned vessel to assist in diagnosis.

CROSS-REFERENCE TO RELATED PATENTS AND APPLICATIONS

[0001] This is a continuation of U.S. application Ser. No. 09/794,5434,filed Feb. 26, 2001, which is a continuation of U.S. application Ser.No. 09/397,836, filed Sep. 16, 1999, now U.S. Pat. No. 6,193,736, whichis a continuation of U.S. application Ser. No. 09/040,058, filed Mar.17, 1998, now U.S. Pat. No. 6,013,030, which is a continuation of U.S.application Ser. No. 08/747,773, filed Nov. 13, 1996, which is acontinuation of U.S. application Ser. No. 08/573,507, filed Dec. 12,1995, now U.S. Pat. No. 5,592,942, which is a continuation of U.S.application Ser. No. 08/285,969, filed Aug. 4, 1994, now U.S. Pat. No.5,485,846, which is a continuation of U.S. application Ser. No.07/906,311, filed Jun. 30, 1992, now U.S. Pat. No. 5,361,768, which areexpressly incorporated herein by reference in their entirety.

FIELD OF INVENTION

[0002] The present invention generally relates to elongate probeassemblies of sufficiently miniaturized dimensions so as to be capableof navigating tortuous paths within a patient's organs and/or vessels.In preferred forms, the present invention is embodied in automated unitswhich are connectable to a probe assembly having a distally locatedultrasound transducer subassembly which enables the transducersubassembly to be positioned accurately by an attending physician andthen translated longitudinally (relative to the axis of the elongateprobe assembly) within the patient under automated control.

BACKGROUND OF THE INVENTION

[0003] I. Introductory Background Information

[0004] Probe assemblies having therapeutic and/or diagnosticcapabilities are being increasingly utilized by the medical community asan aid to treatment and/or diagnosis of intravascular and other organailments. In this regard, U.S. Pat. No. 5,115,814 discloses anintravascular probe assembly with a distally located ultrasonic imagingprobe element which is positionable relative to intravascular sites.Operation of the ultrasonic element in conjunction with associatedelectronic components generates visible images that aid an attendingphysician in his or her treatment of a patient's vascular ailments.Thus, a physician may view in real (or essentially near real) timeintravascular images generated by the ultrasonic imaging probe elementto locate and identify intravascular abnormalities that may be presentand thereby prescribe the appropriate treatment and/or therapy.

[0005] The need to position accurately a distally located operativeprobe element relative to an intravascular site using any therapeuticand/or diagnostic probe assembly is important so that the attendingphysician can confidently determine the location of any abnormalitieswithin the patient's intravascular system. Accurate intravascularposition information for the probe assembly will also enable thephysician to later replicate probe positions that may be needed forsubsequent therapeutic and/or diagnostic procedures. For example, toenable the physician to administer a prescribed treatment regimen overtime and/or to later monitor the effects of earlier therapeuticprocedures.

[0006] Recently ultrasonic imaging using computer-assistedreconstruction algorithms has enabled physicians to view arepresentation of the patient's interior intravascular structures in twoor three dimensions (i.e., so-called three dimensional or longitudinalview reconstruction). In this connection, the current imagereconstruction algorithms employ data-averaging techniques which assumethat the intravascular structure between an adjacent pair of datasamples will simply be an average of each such data sample. Thus, thealgorithms use graphical “fill in” techniques to depict a selectedsection of a patient's vascular system under investigation. Of course,if data samples are not sufficiently closely spaced, then lesions and/orother vessel abnormalities may in fact remain undetected (i.e., sincethey might lie between a pair of data samples and thereby be “masked” bythe image reconstruction algorithms mentioned previously).

[0007] In practice, it is quite difficult for conventional ultrasonicimaging probes to obtain sufficiently closely spaced data samples of asection of a patient's vascular system under investigation since thereconstruction algorithms currently available depend upon the software'sability to process precisely longitudinally separated data samples. Inthis regard, conventional intravascular imaging systems depend uponmanual longitudinal translation of the distally located ultrasoundimaging probe element by an attending physician. Even with the mostskilled physician, it is practically impossible manually to exerciseconstant rate longitudinal translation of the ultrasound imaging probe(which thereby provides for a precisely known separation distancebetween adjacent data samples). In addition, with manual translation,the physician must manipulate the translation device while observing theconventional two dimensional sectional images. This division of thephysician's attention and difficulty in providing a sufficiently slowconstant translation rate can result in some diagnostic informationbeing missed. In order to minimize the risk that diagnostic informationis missed, then it is necessary to devote more time to conducting theactual imaging scan which may be stressful to the patient.

[0008] Thus, what has been needed in this art, is an ultrasound imagingprobe assembly which is capable of being translated longitudinallywithin a section of a patient's vascular system at a precise constantrate. Such an ability would enable a series of corresponding preciselyseparated data samples to be obtained thereby minimizing (if noteliminating) distorted and/or inaccurate reconstructions of theultrasonically scanned vessel section (i.e., since a greater number ofmore closely spaced data samples could reliably be obtained). Also, suchan assembly could be operated in a “hands-off” manner which would thenallow the physician to devote his attention entirely to the real timeimages with the assurance that all sections of the vessel weredisplayed. In terms of reconstruction, the ultrasound imaging probecould be removed immediately and the physician could interrogate theimages or their alternative reconstructions on a near real time basis.Such a feature is especially important during coronary diagnosticimaging since minimal time would be needed to obtain reliable imagingwhile the blood flow through the vessels is blocked by the probeassembly. It is therefore towards fulfilling such needs that the presentinvention is directed.

[0009] II. Information Disclosure Statement

[0010] One prior proposal for effecting longitudinal movements of adistally located operative element associated with an elongate probeassembly is disclosed in U.S. Pat. No. 4,771,774 issued to John B.Simpson et al on Sep. 20, 1988 (hereinafter “Simpson et al '774”). Thedevice disclosed in Simpson et al '774 includes a self-contained motordrive unit for rotating a distally located cutter element via a flexibledrive cable with manual means to effect relative longitudinal movementsof the rotating cutter element.

[0011] More specifically, in Simpson et al '774, the proximal end of aflexible drive cable is slidably coupled to a hollow extension rotarydrive shaft with a splined shaft. The hollow extension drive shaft is,in turn, coupled to a motor, whereas the splined shaft cooperates with amanually operated slide member. Sliding movements of the slide memberrelative to the motor drive unit housing translate into directlongitudinal movements of the flexible drive cable, and hence thedistally located cutter element. In brief, this arrangement does notappear to allow for automated longitudinal movements of the distallylocated probe element.

SUMMARY OF THE INVENTION

[0012] The longitudinal position translator of the present invention isespecially adapted for use with an intravascular probe assembly of typedisclosed in the above-mentioned U.S. Pat. No. 5,115,814 (incorporatedfully by reference hereinto). That is, the preferred intravascular probeassembly with which the position translator of the present invention maybe used will include a flexible guide sheath introduced along a tortuouspath of a patient's vascular system, and a rotatable probe element(preferably an ultrasonic imaging probe) which is operatively introducedinto the lumen of the guide sheath. Of course, the position translatorof the present invention may be modified easily to accommodate lesscomplex one-piece ultrasonic probe assemblies. Rotational movementssupplied by a patient-external motor are transferred to a distallylocated transducer subassembly by means of a flexible torque cable whichextends through the guide sheath.

[0013] As is described more completely in U.S. Pat. No. 5,115,814, theinterior of the guide sheath provides a bearing surface against whichthe probe element rotates. This bearing surface supports the probeelement during its rotation so that virtually no “play” is present—thatis, so that the probe element rotates essentially coaxially relative tothe vascular vessel undergoing therapy and/or investigation. The probeelement is also longitudinally (i.e. axially) movable so thataxial-spaced 360.degree. data sample “slices” of the patient's vascularvessel wall can be imaged.

[0014] The automated longitudinal position translator of the presentinvention generally includes a probe drive module and a lineartranslation module. The probe drive module is most preferably embodiedin an elongate barrel-shaped housing structure having a manualpositioning lever capable of reciprocal movements between advanced andretracted positions. The lever captures a proximal end of the guidesheath within which a probe element is disposed. A flexible torque cableconnects the transducer subassembly at the distal end of the probeelement to a drive shaft which is driven, in the preferred embodiment,by a precision rate-controlled motor located in a separate fixed baseunit. Preferably, the housing is hinged in a “clamshell” fashion to moreeasily facilitate electrical and mechanical coupling of theintravascular probe assembly. The lever may be eliminated when usingless complex one-piece ultrasonic probe assemblies or modified so as tocapture the guide catheter or introducer.

[0015] The linear translation module supports the probe drive module. Inaddition, the linear translation module is coupled operatively to theprobe drive module so as to allow for relative hinged movements therebyand thus permit the probe drive module to be moved between amanually-operable condition (whereby the probe drive module isdisengaged from the longitudinal drive subassembly associated with thelinear translation module to thereby allow a physician to exercisemanual control over the longitudinal positioning of the probe element)and an automated condition (whereby the probe drive module isoperatively engaged with the linear translation module so that automatedlongitudinal position control over the probe element can be exercised).

[0016] In use, the ultrasound imaging probe will be physicallypositioned by an attending physician within a section of a patient'svascular system under investigation using conventional fluoroscopicpositioning techniques. Thereafter, the proximal portion of the probeand guide sheath assembly will be coupled to the probe drive module. Theprobe drive module can then be employed to either manually orautomatically translate the imaging probe element longitudinally withinthe section of the patient's vascular system under investigation duringan ultrasonic imaging scan of the same as may be desired by theattending physician by moving the probe drive module between its manualand automated conditions, respectively. The present invention thusallows the distally located probe element to be rotated, whilesimultaneously providing the attending physician with the capability oflongitudinally translating the probe element at a constant automatedtranslation rate to thereby obtain reliable data samples representativeof longitudinally spaced-apart data “slices” of the patient's vascularsection under investigation. These data “slices” may then bereconstructed using conventional computer-assisted algorithms to presentthe entire section of the patient's vascular system under investigationin a more informative “two-dimensional” longitudinal or“three-dimensional” image display on a CRT (or other) monitor. Thephysician can thus manipulate the image orientation or two-dimensionalsectional plane of the vascular section electronically and therebyachieve a more informative representation of the condition of thepatient's vascular section under investigation.

[0017] In its preferred embodiment, the linear position translatorprovides for automated translation of the imaging probe from a distallocation to a proximal location only. Thus, the imaging probe would notbe advanced under automated control into the guide sheath. Such apreferred functional attribute eliminates the need for sophisticatedsensor and control systems to sense and stop probe advancement should itencounter a “kink” or non-negotiable sharp bend in the guiding sheath.Furthermore, during probe withdrawal (i.e., distal to proximal motion),the guide sheath is supported by the probe and may not “kink”. Also,since the probe has already negotiated all bends during its initialmanual distal advancement, the attending physician is assured that thebends are in fact negotiable by the probe upon its withdrawal throughthat same path. Thus, although the preferred embodiment contemplatesautomated longitudinal translation in a proximal direction, it islikewise preferred that the attending physician advance the probe in adistal direction manually so that the physician may use his or herexperience with the catheters and the tactile sensations to judge whenan obstruction has been encountered.

[0018] Further features and advantages of the present invention willbecome more clear after careful consideration is given to the followingdetailed description of presently preferred exemplary embodiments.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0019] Reference will hereinafter be made to the accompanying drawingswherein like reference numerals throughout the various FIGURES denotelike structural elements, and wherein;

[0020]FIG. 1 is a schematic view of an ultrasonic imaging system thatincludes an automated longitudinal position translator according to thepresent invention;

[0021]FIG. 2 is a top plan view of the probe drive module employed withthe longitudinal position translator according to the present inventionshowing the housing thereof in an opened state;

[0022]FIG. 3 is a side elevation view, partly in section, of the probedrive module shown in FIG. 2;

[0023]FIGS. 4A and 4B are each side elevation views of the longitudinalposition translator according to the present invention in its automatedand manual conditions, respectively;

[0024]FIGS. 5A and 5B are each top plan views of the longitudinalposition translator according to the present invention in its automatedand manual conditions, respectively;

[0025]FIGS. 6A and 6B are each front end elevational views of thelongitudinal position translator according to the present invention inits automated and manual conditions, respectively;

[0026]FIG. 7 is a partial side elevational view which is also partly insection of the longitudinal position translator according to the presentinvention; and

[0027] FIGS. 8A-8C are top plan views of the longitudinal positiontranslator according to this invention which schematically depict apreferred mode of automated operation.

DETAILED DESCRIPTION OF THE PREFERRED EXEMPLARY EMBODIMENTS

[0028] A schematic diagram of an exemplary ultrasound imaging system 10is shown in accompanying FIG. 1. System 10 generally includes anultrasound imaging probe assembly 12 having a guide sheath 14 and adistally located ultrasound imaging probe element 16 inserted into thelumen of guide sheath 14, the probe element 16 being depicted in FIG. 1as being visible through the guide sheath's transparent wall. Theultrasonic imaging probe assembly 12 preferably embodies those featuresmore fully described in the above-identified U.S. Pat. No. 5,115,814.

[0029] The overall length of the imaging probe assembly 12 is suitablefor the desired diagnostic and/or therapeutic intravascular procedure.For example, the overall length of the probe assembly 12 may be shorterfor direct (e.g., arteriotomy) insertions as compared to the length ofthe probe assembly 12 needed for percutaneous distal insertions (e.g.,via the femoral artery). A representative length of the imaging probeassembly 12 is therefore shown in the accompanying drawings for clarityof presentation.

[0030] The terminal end of the guide sheath 14 preferably carries aradiopaque marker band 18 formed of gold or other fluoroscopicallyvisible material. The marker band 18 allows the attending physician tomonitor the progress and position of the guide sheath 14 duringintravascular insertions using standard fluoroscopic imaging techniques.

[0031] The proximal end of the imaging probe assembly 12 is receivedwithin a probe drive module 20. In essence, the probe drive module 20includes a distally open-ended and longitudinally barrel-shaped housing22, and a positioning lever 24 which captures the proximal end of theguide sheath 14. The proximal end of the ultrasound imaging probeelement 16 is mechanically and electrically connected to the probe drivemodule 20. Longitudinal reciprocal movements of the positioning lever 24relative to the housing 22 will thus in turn effect relativelongitudinal displacements of the distal end of the probe element 16within the guide sheath 14 relative to the longitudinal axis of theprobe assembly 12.

[0032] The probe drive module 20 also includes a drive unit 26 fixedlyconnected proximal to the housing 22 and contains the structures whichsupply mechanical rotation and electrical signals to the probe element16. In the preferred embodiment, mechanical rotation of the probeelement 16 is provided by a separate precision motor 28 associated witha base unit (not shown) and operatively coupled to the probe drivemodule 20 via a flexible drive cable 28 a. It is entirely conceivable,however, that the drive unit 26 could be sized so as to accommodate themotor 28.

[0033] The drive unit 26 is most preferably configured so that theattending physician may comfortable grasp its exterior with one handwhile the probe drive module 20 is in its manual condition. The driveunit 26 thus forms a handle which allows the physician to manuallymanipulate the relative position between the housing 22 and thepositioning lever 24 thereby responsively permitting manual longitudinalmovements to be imparted to the probe element 16. A thumb/finger switch30 may thus be manually depressed to allow the physician to selectivelyoperate the drive unit 26 and thereby rotate the ultrasonic imagingprobe element 16 when it is desired to conduct an ultrasonic imagingscan. Electrical connection between the switch 30 and the controlconsole 46 is made via I/O cabling 41.

[0034] During rotation, electrical communication is established betweenthe transducer subassembly in the distal end of the ultrasonic imagingprobe element 16 and the ultrasound transceiver 40 via patient-internalelectrical coaxial cabling (not shown) within the probe element 16,drive unit 26 and electrical patient-external I/O cabling 41. Theultrasound transceiver 40 produces a pulse signal (of desired magnitudeand shape) which is applied via the electrical cabling 41 to anelectroacoustic transducer associated with the distal end of the probeelement 16. The transceiver 40 also performs conventional signalprocessing operations (e.g., amplification, noise reduction and thelike) on electrical signals generated by the electromechanicalexcitation of the transducer within the probe element 16 (i.e., signalsgenerated by the transducer in response to receiving acoustic echowaves).

[0035] These signals are further processed digitally via known displayalgorithms (e.g., conventional PPI (radar) algorithms) and are thensupplied as input to a CRT monitor 42 (or any other equivalent displaydevice) so as to generate an ultrasound image 44 of desired formatrepresentative of the vascular structures reflecting ultrasonic energytoward the transducer within the distal end of the probe element 16. Acontrol console 46 may be employed by the attending physician so as toselect the desired operational parameters of the ultrasound transceiver40 and/or the display format of the image 44 on the CRT 42, for example.

[0036] The probe drive module 20 is operatively coupled to and supportedby the linear translation module 48 so as to allow for reciprocalrectilinear movements of the housing 22/drive unit 26 relative to boththe linear translation module 48 and the positioning arm 24 whichcollectively remain in a fixed position as will be described in greaterdetail below. As will also be described in greater detail below, theprobe drive module 20 is mounted for hinged movements relative to thelinear translation module 48 between a manually-operable condition(whereby the probe drive module 20 is operatively disengaged from themotor driven translator associated with the linear translation module48) and a automatically-operable condition (whereby the probe drivemodule 20 is operatively engaged with the motor driven translatorassociated with the linear translation module 48).

[0037] The linear translation module 48 includes a proximal housing 48 awhich contains appropriate speed-reducers, drive shafts and associatedcouplings to be described below in connection with FIG. 7. Suffice it tosay here, however, that driven power is provided to the structuresinternally of housing 48 a by a separated precision motor 50 associatedwith a system base unit (not shown) which is coupled operatively to thestructures internally of housing 48 a via a flexible drive shaft 50 a.Again, it is entirely conceivable that the housing 48 a of the lineartranslation module 48 could be sized and configured so as to accomodatethe motor 50. Automated operation of the motor 50 (and hence the lineartranslation module 48) may be accomplished through the selection ofappropriate operation parameters by the attending physician via controlconsole 46. Operation of both the linear translation module 48 and theprobe drive module 20 may be initiated by depressing the foot-switch 27.

[0038] The exemplary probe drive module 20 which is employed in thepresent invention is perhaps more clearly depicted in accompanying FIGS.2 and 3. As is seen, the housing 22 is collectively formed of a pair ofelongate lower and upper housing sections 51, 52, respectively, whichare coupled to one another along adjacent longitudinal edges in aclamshell-hinged arrangement via hinge pin 54.

[0039] It will be noticed with particular reference to FIG. 2 that theproximal and distal ends 54 a, 54 b of pin 54 are rigidly fixed to theproximal and distal ends 51 a, 51 b of housing section 51, respectively,while the housing section 52 is pivotally coupled to the pin 54 (andhence the housing section 51) by means of proximal and distal andintermediate pivot fsleeves 56 a, 56 b and 56 c, respectively. Thehousing sections 51, 52 are maintained in their closed state (i.e., asshown in FIGS. 4A through 5B) by means of a spring-loaded detent 57 a(see FIG. 2) which may be moved into and out of an aperture (not shown)formed in the housing section 51 via operating lever 57 b.

[0040] The positioning lever 24 is oriented transversely relative to theelongate axis of housing 22. In this regard, the lever 24 includes asleeve end 24 a which is coupled to the pivot pin 54 to allow reciprocallongitudinal and pivotal movements of the lever 24 to occur relative tothe longitudinal axis of pin 54. The opposite end 24 b of lever 24extends radially outwardly from the housing 22.

[0041] The housing 22 defines an elongate slot 58 when the housingsections 51, 52 are in a closed state (i.e., as depicted in FIG. 1). Theslot 58 allows the positioning lever 24 to be manually moved along thelongitudinal axis of pin 54 during use (i.e., when the housing sections51, 52 are in a closed state) between retracted and extended positions(shown respectively by phantom line representations 24′ and 24″ in FIG.2). The retracted position 24′ of lever 24 is established by a distalface of a pivot sleeve 56 c integral with the housing section 52 andpivotally coupled to pin 54 in a manner similar to pivot sleeves 56 aand 56 b. On the other hand, the extended position 24″ of lever 24 isestablished by a proximal face of pivot sleeve 56 b.

[0042] The lever 24 is supported by a concave inner surface 59 formed inthe housing section 51 when the housing sections 51 and 52 are in aclosed state. The inner surface 59 provides a bearing surface againstwhich the lever 24 slides during the latter's movement between itsretracted and extended positions 24′ and 24″, respectively.

[0043] A scale 60 (see FIGS. 4A and 5A) preferably is provided on thehousing 22. A pointer 24 c associated with the lever 24 may be alignedwith the scale 60 to provide an attending physician with informationregarding the position of probe element 16 relative to its most distalposition within the guide sheath 14. That is, longitudinal movement oflever 24 an incremental distance (as measured by pointer 24 c and thescale 60) will effect movement of the probe element 16 relative to itsmost distal position within the guide sheath's distal end by that sameincremental dimension.

[0044] Accompanying FIG. 2 also more clearly shows the cooperativeengagement between positioning lever 24 and the proximal end of guidesheath 14. In this regard, it will be noted that the proximal end ofguide sheath 14 includes a side-arm port 70 which extends generallytransverse to the longitudinal axis of guide sheath 14. Side-arm port 70includes a conventional Leur-type locking cap 72 that is coupledcoaxially to a similar locking cap 74 associated with the proximal endof guide sheath 14. Side-arm port 70 is thus in fluid-communication withthe lumen of guide sheath 14 so that saline solution, for example, maybe introduced via side-arm tubing 70 a.

[0045] A shaft extension 75 of probe element 16 and electrical cablingcoaxially carried thereby are mechanically and electrically coupled tothe output shaft 77 of the probe drive module 20 via coaxial cablecouplings 75 a and 75 b. It will be appreciated that coaxial cablingwithin the flexible torque cable portion of probe element 16 (not shown)will rotate with it as a unit during operation, but that the electricalI/O signals will be transferred to transceiver 40 by means of couplings75 a and 75 b. The manner in which the separate electrical I/O path(represented by cable 41—see FIG. 1) and mechanical input path(represented by the flexible drive shaft 28 a—see FIG. 1) are combinedinto a common electrical/mechanical output path (represented by outputshaft 77) will be explained in greater detail with reference to FIG. 3.

[0046] The shaft extension 75 is preferably fabricated from a length ofconventional stainless steel hypodermic tube and is rigidly coupled atits distal end to a flexible torque cable (not shown). As mentionedbriefly above, the torque cable extends the length of the guide sheath14 and is connected at its distal end to a transducer subassembly in thedistal end of the probe element 16. The torque cable thereby transfersthe rotational motion imparted via the motor to shaft extension 75 ofthe probe element 16 causing the transducer subassembly to similarlyrotate within the lumen of the guide sheath 14 near the guide sheath'sdistal end, as well as to be longitudinally shifted within guide sheath14 via manipulation of the relative position of the arm 24.

[0047] The shaft extension 75 extends through an end cap 76 which iscoupled coaxially to locking caps 72 and 74. End cap 76 houses asynthetic resin bearing element (not shown) which serves as a proximalrotational bearing for the shaft 75, and also serves to seal theproximal end of guide sheath 14 against fluid (e.g., saline liquid)leakage.

[0048] Lever 24 defines a pair of mutually transverse concave cradlesurfaces 80 and 82. The longitudinal dimension of cradle surface 80 isoriented parallel to the longitudinal dimension of housing 22, whereascradle surface 82 (which is joined at one of its ends to the cradlesurface 80) is oriented transverse to the longitudinal dimension ofhousing 22 (i.e., since it is traverse to cradle surface 80).

[0049] Cradle surface 80 is sized and configured so as to accommodate anexterior surface portion of coaxially locked caps 72, 74 and 76. Cradlesurface 82, on the other hand, is sized and configured to acceptside-arm port 70 and side-arm tubing 70 a extending therefrom. Anaxially extending inner concave surface 84 is defined in housing section52 and, like cradle surface 82, is sized and configured so as to acceptan exterior portion of locking caps 72, 74 and 76.

[0050] When housing sections 51 and 52 are in a closed state, caps 72,74 and 76 will be enveloped by housing 22. More specifically, innerconcave surface 84 will positionally restrain caps 72, 74 and 76 withincradle surface 80 when housing sections 51 and 52 are closed. Sinceside-arm port 70 will likewise be positionally restrained within cradlesurface 82 when housing sections 51, 52 are closed, caps 72, 74 and 76will be moved longitudinally as a unit with position lever 24. That is,longitudinal movements of lever arm 24 between its retracted andextended positions will cause the proximal end of guide sheath 14 (i.e.,coaxially mounted caps 72, 74 and 76) to be longitudinally movedrelative to the longitudinally stationary (but axially rotatable) shaftextension 75. In such a manner, the proximal end of guide sheath 14 willbe moved closer to and farther from the open distal end of housing 22.

[0051] As can be seen in FIG. 3, the interior of the drive unit 26 ishollow to house electrical/mechanical coupling assembly 85.Electrical/mechanical coupling 85 combines an electrical inputpath—represented by coaxial I/O cable 41 which establishes electricalcommunication with transceiver 40—and a mechanical inputpath—represented by flexible drive shaft 28 a associated with motor 28(see FIG. 1) into a common coaxial output shaft 77.

[0052] Output shaft 77 is rotatably held within bearing block 86 andincludes a rearwardly extending rotatable tail portion carrying a numberof electrical slip-rings 86 a. Electrical communication between theslip-rings 86 a and coupling 75 b is established by a length of coaxialcable (not shown) housed within the output shaft 77. Stationary brushes88 a in sliding electrical contact with respective ones of theslip-rings 86 a are associated with a brush block 88. Lead wires 88 bare, in turn, coupled electrically at one end to brush block 88 (andhence to coaxial connector 75 a via brushes 88 a and slip-rings 86 a),and at the other end to coaxial I/O cable 41 via a ferrite coiltransformer (not shown). Slip-rings 86 a, brushes 88 a, brush block 88,lead wires 88 b, and ferrite core transformer (not shown) are housedwithin a common electrically shielded enclosure 90.

[0053] The mechanical input path generally represented by flexible driveshaft 28 a is coupled operatively to one end of a rigid rotatable driveshaft 92 carrying a drive gear 94 at its other end. Drive gear 94 is, inturn, meshed with a gear 96 carried by output shaft 77. Upon rotation ofdrive shaft 92, meshed gears 94, 96 will cause shaft 77 to responsivelyrotate. Preferably, gears 94 and 96 are in a 1:1 ratio, but other gearsizes (and hence ratios) may be provided if desired.

[0054] The probe drive unit 20 is mounted for reciprocal rectilinearmovements to the linear translation module 48 as is shown inaccompanying FIGS. 4A through 6B. In this regard, the linear translationmodule includes a base plate 100 which supports the housing 48 a and itsinternal structures (to be described below with reference to FIG. 7).The probe drive module 20 itself includes a longitudinally spaced-apartpair of support flanges 102, 104, each of which is slidably mounted ontoa pair of parallel guide rails 106, 108.

[0055] The proximal end of guide rail 106 is pivotally connected to thehousing 48 a while its distal terminal end is pivotally connected to anupright support block 106 a. A forward and rearward pair of transversesupport arms 110, 112 each having one end rigidly coupled to guide rail106 and an opposite end rigidly coupled to the guide rail 108. Thus, thesupport arms 110, 112 are capable of pivoting between a lowered position(e.g., as shown in FIGS. 4A, 5A and 6A) and a raised position (e.g., asshown in FIGS. 4B, 5B and 6B) by virtue of the pivotal guide rail 106 soas to, in turn, pivotally move the probe drive module 20 between itsautomatically-operable condition and its manually-operable condition,respectively, due to its attachment to the guide rails 106, 108 viasupport flanges 102, 104.

[0056] The ends of each transverse support arm 110, 112 between whichthe guide rail 108 is fixed are removably captured by uprightrestraining posts 114, 116, respectively. As is perhaps more clearlyshown in FIGS. 6A and 6B, the restraining posts 114, 116 (onlyrestraining post 114 being visible in FIGS. 6A and 6B) are rigidlysupported by the base plate 100 and include an inwardly projecting lip114 a, 116 a which provide an interference fit with the terminal ends ofsupport arms 110, 112, respectively. In this connection, it is preferredthat the restraining posts 114, 116 be formed of a relatively stiff, butresilient plastics material (e.g., nylon, polyacetal or the like) sothat when the probe drive unit is moved between itsautomatically-operable and manually-operable conditions, the posts 114,116 are capable of yielding somewhat to allow such movement.

[0057] The positioning arm 24 of the probe drive unit 20 is fixedly tiedto the forward transverse support arm 110 by an upright connector 120 aon a longitudinal connector 120 b. In this regard, the upper end ofupright connector 120 a extends through a longitudinal slot on the sideof the housing 22 opposite slot 58 and positionally captures the ends ofthe positioning arm 24 around pin 54. The lower end of the uprightconnector 120 a is connected to the distal end of the horizontallydisposed longitudinal connector 120 b. The proximal end longitudinalconnector 120 b is, in turn, rigidly fixed to the transverse support arm110 by any suitable means (e.g., screws). It will be understood,therefore, that the position of the positioning arm 24 (and hence theguide sheath 14) remains fixed relative to the base 100 of the lineartranslation module 48 during longitudinal movements of the probe drivemodule 20 along the guide rails 106 and 108. Thus, the relative positionof the patient-internal transducer subassembly at the distal end of theprobe element 16 will correspondingly shift the same distance as theprobe drive module 20 relative to the patient internal distal end of theguide sheath 14.

[0058] Automated longitudinal shifting of the probe drive module 20 (andhence the ultrasonic transducer subassembly at the distal end of theprobe element 16) is ermitted by the coaction between a longitudinallyextending drive screw 120 and a threaded collar portion 122 (see FIGS.4B and 7) associated with the support flange 102 of the probe drivemodule 20. The distal and proximal ends of the drive screw 120 arerotatably supported by an upright distal bearing block 124 and anupright proximal bearing block 126 (see FIG. 7), respectively.

[0059] As can be seen in FIGS. 4B, 5B, 6B and 7, the threaded collarportion 122 is disengaged from the threads of drive screw 120 when theprobe drive module 20 is in its manually-operable condition. As aresult, the attending physician may simply manually shift the probedrive module 20 longitudinally along the guide rails 106, 108. When theprobe drive module 20 is pivoted into its automatically-operablecondition as shown in FIGS. 4A, 5A and 6A, the threads associated withthe threaded collar portion 122 will be mateably engaged with thethreads of the drive screw 120. As a result, rotation of the drive screw120 about its longitudinal axis will translate into longitudinaldisplacement of the probe drive module 20. The threads of the drivescrew 120 and the threaded collar portion 122 as well as the rotationdirection of the drive screw 120 are most preferably selected so as toeffect longitudinal shifting of the probe drive module from the distalend of the drive screw towards the proximal end thereof—i.e., a distalto proximal displacement. However, these parameters could be changed soas to effect a reverse (proximal to distal) displacement of the probedrive unit, if necessary or desired.

[0060] The drive screw 120 is coupled operatively to the flexible driveshaft 50 a (and hence to the driven output of motor 50) by thestructures contained within housing 48 a. In this regard, the proximalend of the drive screw is coupled to the output shaft of a speed reducer128 via a shaft coupling 130. The input to the speed reducer 128 is, inturn, coupled to the flexible drive shaft 50 a from a rigid shaftextension member 132 and its associated shaft couplings 132 a and 132 b.The speed reducer 128 is of a conventional variety which provides apredetermined reduced rotational speed output based on the rotationalspeed input. Preferably, the motor 50, speed reducer 128 and drive screw120 are designed so as to effect longitudinal translation of the probedrive unit 20 at a rate of between about 0.25 to 1.0 mm/sec. Of course,other longitudinal translation rates may be provided by varying theparameters of the motor 50, speed reducer 128 and/or drive screw 120.

[0061] In use, the attending physician will preposition the guide sheath14 and imaging probe element 16 associated with the ultrasound imagingprobe assembly 12 within the vessel of the patient to be examined usingstandard fluoroscopic techniques and/or the techniques disclosed in theabove-mentioned U.S. Pat. No. 5,115,814. Once the guide sheath14/imaging probe element 16 have been prepositioned in a region of thepatient's vessel which the physician desires to observe, the proximalend of the probe assembly 12 will be coupled to the probe drive module20 in the manner described above. Thereafter, the physician may conductan ultrasound scan of the patient's vessel by operating switch 30 tocause high-speed rotation of the transducer subassembly on the distalend of the probe element 16 within the guide sheath 14. Data samplesassociated with different transverse sections of patient's vessel maythen be obtained by the physician manually shifting the probe drivemodule 20 along the guide rails 106, 108 in the manner described above.

[0062] Alternatively, the physician may elect to pivot the probe drivemodule 20 into its automatically-operable condition and then selectautomated operation of the same via the control console 46 andfoot-switch 27. In such a situation, the probe drive module (and hencethe transducer subassembly at the distal end of the probe element 16)will be shifted longitudinally at a constant rate simultaneously withhigh-speed rotation of the transducer subassembly. In this manner, datasamples representing longitudinally spaced-apart 360.degree. “slices” ofthe patient's interior vessel walls will be accumulated which can thenbe reconstructed using known algorithms and displayed in“two-dimensional” or “three-dimensional” formats on the monitor 42.

[0063] Accompanying FIGS. 8A-8C schematically depict the longitudinaltranslator according to this invention being operated in an automatedmanner. In this connection, and as was noted briefly above, the probedrive module 20 is most preferably translated in a distal to proximaldirection by means of the linear translation module 48 (i.e., in thedirection of arrows 140 in FIGS. 8A and 8B). In FIG. 8A, the probe drivemodule is shown in a position at the beginning of an automatedultrasonic imaging scan, it being noted that the pointer 24 c associatedwith the positioning arm 24 registers with the zero marking on the scale60. The physician will then initiate automated ultrasonic scanning viathe foot-switch 27 which causes the probe drive unit 20 to be displacedproximally (arrow 140) at a constant rate as shown in FIG. 8B. Thisproximal displacement of the probe drive module 20 will, in turn, causethe transducer subassembly on the distal end of the probe element 16 tobe longitudinally displaced proximally (i.e., pulled back away from) thedistal-most end of the guide sheath 14.

[0064] The ultrasonic imaging scan is automatically terminated (e.g., byuse of suitable limit switches and/or position transducers) when theprobe drive unit reaches the its most proximal position as shown in FIG.8C. In this connection, the present invention most preferably isprovided with a limit switch (not shown) enclosed within a limit switchhousing 29 (see FIGS. 4a and 5B) which is mechanically actuated whensupport flange 102 contacts support arm 112 (i.e., when the probe drivemodule 20 is in its most proximal position). The limit switch in housing29 communicates electrically with the control console 46 via cabling 41.Virtually any suitable equivalent position-sensing devices could beemployed in place of the limit switch. For example, the housing 29 couldbe sized and configured to accommodate an absolute position transducerso as to communicate absolute position to the control console 46. Theinformation provided by such an absolute position transducer could beemployed in conjunction with modified reconstruction algorithms forimage reconstruction, even during manual operation of the probe drivemodule 20.

[0065] Upon the probe drive module 20 reaching its most proximalposition, the pointer 24 c associated with the positioning arm 24registers with the marking “10” on the scale 60 of housing 22. Ofcourse, the ultrasonic imaging scan need not necessarily be conductedover the entire range of 0-10 marked on the scale 60 and thus could beterminated at any time by the physician simply releasing the foot-switch27 or by simply pivoting the probe drive module 20 into itsmanually-operable condition.

[0066] Those skilled in this art will recognize that a number ofequivalent mechanical and/or electrical means could be employed. Forexample, locking slides, latches and quarter-turn screws could be usedto allow engagement and disengagement of the probe drive module with thelinear translation module. A flexible drive shaft connects the lineartranslation module to a rate-controlled motor which controls theautomatic linear translation rate. The motor is most preferably locatedin a separate fixed base unit, but could be provided as in an integralpart of the linear translation module, if desired.

[0067] Furthermore, various translation rates associated with the motormay be selected for various purposes. For example, slow rates give ampletime for the physician to examine the real-time images in cases wheretime is not a limiting factor. The rate upper limit is governed by theprobe rotation rate and the effective thickness of the imaging dataslices generated by the probe, such that there is no (or an acceptable)gap between successive imaging data slices. This would prevent missingdiscernible features during vascular imaging with automatic translation.The effective thickness is governed by the ultrasonic beamcharacteristics of the probe. For some applications, the translation maybe discontinuous (i.e., gated to an electrocardiogram) for use withmodified algorithms or programmed to translate a fixed distancediscontinuously.

[0068] Thus, while the invention has been described in connection withwhat is presently considered to be the most practical and preferredembodiment, it is to be understood that the invention is not to belimited to the disclosed embodiment, but on the contrary, is intended tocover various modifications and equivalent arrangements included withinthe spirit and scope of the appended claims.

What is claimed is:
 1. A catheter comprising a motorized positiontranslator coupled to a cable, wherein said position translator isadapted for both manual linear translation of the cable relative to thecatheter and motor-driven linear translation of the cable relative tothe catheter.
 2. The catheter of claim 1, wherein the positiontranslator is electrically connected to a foot-activated switch toresponsively effect said motor-driven linear translation of said cablewhen said switch is activated.
 3. The catheter of claim 1, wherein thecable comprises an imaging instrument.
 4. The catheter of claim 3,wherein the imaging instrument comprises an ultrasound transducer. 5.The catheter of claim 1, wherein the motorized position translatorcomprises a drive module, said drive module comprising a distallyopen-ended and longitudinally barrel-shaped housing and a positioninglever.
 6. A method for imaging a patient's body cavity, comprising thesteps of: providing a catheter having a motorized position translatorcoupled to a cable, wherein said position translator is adapted for bothmanual linear translation of the cable relative to the catheter andmotor-driven linear translation of the cable relative to the catheter;positioning the catheter within a region of interest within thepatient's body cavity; and translating the cable relative to thecatheter.
 7. The method of claim 6, wherein the cable comprises animaging instrument.
 8. The method of claim 7, wherein the imaginginstrument comprises an ultrasound transducer.
 9. The method of claim 8,further comprising the step of radially rotating the cable.
 10. Themethod of claim 9, wherein the radial rotation is motor driven.
 11. Amethod of performing an ultrasonic imaging scan comprising the steps of:providing a catheter comprising a cable having an ultrasound transducercoupled to its distal portion; providing a motorized position translatorcoupled to the cable, wherein said position translator is adapted forboth manual linear translation of the cable relative to the catheter andmotor-driven linear translation of the cable relative to the catheter;positioning the ultrasound transducer in a region of interest within ananatomical structure of a patient; radially rotating the cable thusrotating the ultrasound transducer; and activating the to effect lineartranslation of the ultrasound transducer.
 12. The method of claim 11,wherein the ultrasound transducer is in electrical communication with anultrasound transceiver, said transceiver being in electricalcommunication with a monitor, and wherein the method further comprisesthe steps of: receiving a signal transmitted by the ultrasoundtransducer, said signal being representative of the region of interest;processing the signal by applying a display algorithm to said signal;transmitting the processed signal to the monitor; and displaying anultrasound image on the monitor, said image representative of the regionof interest.
 13. The method of claim 11, wherein the ultrasoundtransducer is in electrical communication with an ultrasoundtransceiver, said ultrasound transceiver being in electricalcommunication with a control console, wherein the method furthercomprises the step of using the control console to select operationalparameters of the ultrasound transceiver.
 14. The method of claim 11,wherein a control console is in electrical communication with the motor,and wherein the method further comprises the step of using the controlconsole to select the linear translation speed of the motor.